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Alaska Fisheries Technical Report Number 86, June 2005 U.S. Fish and Wildlife Service Migratory Patterns of Different Spawning Aggregates of Dolly Varden in the Kenai River Watershed Douglas E. Palmer and Bruce E. King Abstract Radiotelemetry was used to monitor the seasonal movements of adult Dolly Varden Salvelinus malma in the Kenai River watershed. Dolly Varden from spawning aggregates in Cooper Creek (N=20), Quartz Creek (N=60), South Fork of the Snow River (N=60) and the upper Kenai River (N=79) were implanted with radio transmitters and tracked for varying periods from September 1998 through December 2001. Nearly half (N=109) of the radio-tagged Dolly Varden provided movement information for one year or longer. All radio-tagged Dolly Varden migrated seasonally between lake and riverine habitats to fulfill critical habitat needs. Lacustrine habitats were selected for winter refuge with Kenai and Skilak lakes providing the majority of overwinter habitat. Movement to overwintering lakes began in October and was complete by December. Movement from overwintering lakes to summer feeding areas began in May. Patterns of movement during the summer months were different for each spawning aggregate, but were generally associated with the timing and location of smolting or spawning salmon. Most radio-tagged fish were found in riverine habitats from June through September except for fish from the Snow River spawning aggregate which remained in Kenai Lake through mid-summer. The Killey River was an important early summer feeding area for many fish, but by August most fish were found in the Kenai River above and below Skilak Lake. Fish were located at spawning areas from late September through October. Although a few fish spawned during consecutive years, it appears that most Dolly Varden from these spawning aggregates will skip a year or two between spawning. Introduction The Kenai River provides a variety of recreational fishing opportunities and receives more angler effort than any other river in Alaska (Howe et al. 2001d). Although most anglers participate in popular sport fisheries targeting Chinook salmon Oncorhynchus tshawytscha, sockeye salmon O. nerka, coho salmon O. kisutch, and rainbow trout O. mykiss, the Kenai River also supports a major fishery for Dolly Varden Salvelinus malma. Catches of Dolly Varden in the Kenai River have ranged from 34,577 to 107,785 fish annually since 1990 (Appendix 1; Mills 1991–1994; Howe et al. 1995, 1996, 2001a–d, Walker et al. 2003, Jennings et al. 2004). Dolly Varden are caught throughout the Kenai River, however, anglers targeting this species generally concentrate their efforts above Skilak Lake and in the middle Kenai River above the Moose River. Catches of Dolly Varden in these sections have comprised about 74% of the total catch in the Kenai River since 1990. Angler effort directed at Dolly Varden in the upper and middle Kenai River has increased substantially in recent years. An increase in angler effort, coupled with a perception by the Authors: Douglas E. Palmer is a senior fishery biologist with the U.S. Fish and Wildlife Service. He is the corresponding author and can be contacted at the Kenai Fish and Wildlife Field Office, P.O. Box 1670, Kenai, Alaska; or [email protected]. Bruce E. King is currently retired but was formerly a fisheries research biologist with the Alaska Department of Fish and Game in Soldotna, Alaska. Alaska Fisheries Technical Report Number 86, June 2005 U.S. Fish and Wildlife Service public that harvest was increasing and that numbers of Dolly Varden were declining, generated concern about negative impacts to the population. Because no data were available regarding stock status, the Alaska Board of Fisheries responded to this concern beginning in 1990 with a series of more restrictive regulations for Dolly Varden in the Kenai River watershed (Gamblin et al. 2004). Regulation changes included a reduction in bag/possession limit, size restrictions, and spawning season closures in three tributary streams. Concern over potential negative impacts to Dolly Varden populations in the Kenai River and the lack of base population data prompted the development of a cooperative study between the U.S. Fish and Wildlife Service and the Alaska Department of Fish and Game. The primary focus of the study was to use radiotelemetry to describe the extent and patterns of movement of Dolly Varden in the Kenai River watershed. Preliminary investigations in 1996 and 1997 focused on identification of spawning aggregates of Dolly Varden in the upper Kenai River watershed. Spawning aggregates were identified in Cooper Creek, Quartz Creek, South Fork of the Snow River, and the upper mainstem Kenai River. This report describes the seasonal distribution and migratory patterns of Dolly Varden from these spawning aggregates. Radio transmitters used during the study provided up to two years of location data that also allowed us to examine frequency of spawning and fidelity to overwintering habitats. Study Area The Kenai River drainage encompasses approximately 5,500 km2 on the Kenai Peninsula in South-central Alaska (Figure 1). The Kenai River is glacially fed and originates at the outlet of Kenai Lake. The upper reach of the Kenai River is about 27 km long and extends from Kenai Lake to the inlet of Skilak Lake. The river traverses Skilak Lake for about 24 km, and then flows another 17 km to Naptowne Rapids. Below Naptowne Rapids, the river flows another 63 km to Cook Inlet. Discharge in the Kenai River depends on the outflow of Kenai and Skilak lakes and lacks the flow extremes characteristic of streams without headwater lakes. The mean annual discharge in the Kenai River at Soldotna is approximately 167 m3/s with summer flows ranging from 142 to 850 m3/s (Bigelow et al. 1985). Glacial melt produces turbid conditions throughout the year, but water clarity improves during winter months when flows range from 23 to 142 m3/s. Major tributaries that enter the Kenai River above Naptowne Rapids include the Killey River which empties into the Kenai River at river kilometer (rkm) 70.8, Skilak River which contributes melt water from Skilak Glacier at the east end of Skilak Lake, Russian River (rkm 118.7), Cooper Creek (rkm 127.4), and Juneau Creek (rkm.127.8). Major tributaries to Kenai Lake include Quartz Creek, Trail River, Ptarmigan Creek, and the Snow River. Methods Dolly Varden in spawning condition were surgically implanted with radio transmitters during 1998 and 1999 (Appendix 2). During 1998, transmitters were implanted in Dolly Varden that were spawning in Cooper and Quartz creeks and the South Fork of the Snow River. Radio- tagging efforts during 1999 focused on Dolly Varden spawning in the upper Kenai River above Jim’s Landing. The majority of fish were captured with hook-and-line, however drift gill nets (7.6 mm stretch mesh) were also fished in the upper Kenai River to capture fish for radio transmitter implants. 2 Alaska Fisheries Technical Report Number 86, June 2005 U.S. Fish and Wildlife Service Summit Juneau Creek Beaver Devils Creek Quartz Creek Creek Creek Upper Moose Kenai River River Tern Kenai Lake Bing’s Jim’s Landing Daves Creek Cook Landing Soldotna Trail Inlet River Naptowne Ptarmigan Creek Rapids Kenai Lake Skilak Lake Russian 3 River Skilak Snow River River Cooper Funny Creek River Killey River N South Fork Snow River Benjamin Creek 10 0 10 20 Kilometers FIGURE 1.─Map of the Kenai River watershed. Shaded areas indicate locations where Dolly Varden were captured and implanted with radio transmitters during 1998 and 1999. Alaska Fisheries Technical Report Number 86, June 2005 U.S. Fish and Wildlife Service Implanting Transmitters Dolly Varden were anesthetized with a 30-mg/L solution of clove oil. Unconscious fish were placed ventral side up in a neoprene-lined cradle, and their gills were irrigated with a combination of anesthesia and oxygenated water during the procedure. A 2–3-cm incision large enough to accommodate the transmitter was made anterior to the pelvic girdle approximately 1 cm from the midventral axis. The transmitter antenna was routed under the pelvic girdle and through the body wall slightly off the midventral axis and anterior to the vent using a hypodermic needle and grooved director. Oxytetracycline was administered intraperitoneally at a dosage of 0.5 mg/kg body weight to help prevent infection. The incision was closed with three or four individual stitches of absorbable suture and Vetbond® adhesive. Surgical instruments and transmitters were soaked in a cold sterilant and rinsed in saline solution before use. Each surgery averaged 6 min, and fish were swimming upright and respiring normally within 3–5 min of being returned to a freshwater holding tank. Fish were released near the capture site once they gained equilibrium and were actively swimming. Surgical implant procedures were similar to those described by Summerfelt and Smith (1990). Radio transmitters (Lotek® model CFRT–3EM) were 48 mm in length and 10 mm in diameter and equipped with a 30-cm plastic coated wire antenna. Each transmitter weighed 8.1 g in air and never exceeded 2% of fish weight (Winter 1983). All transmitters had a 5 second burst rate for 8 hours each day. This duty cycle provided an estimated transmitter life of 635 days. Each transmitter emitted a unique digital signal on one of ten frequencies between 149 and 151 MHZ. Radio-Tracking Procedures Movements of radio-tagged Dolly Varden were documented using a combination of aerial and ground-based surveys. Receivers used for tracking were the SRX 400 receiver/datalogger (Lotek Engineering Incorporated®). A portable global positioning system (GPS) was used to determine the latitude and longitude of each located fish. Ground-based tracking was conducted from boats, highway vehicles, all-terrain vehicles (ATV), and on foot.

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